Quantifying Coronal Dimming as Observed in EUV and X-ray Images in Eruptive Events

Data from SOHO have shown that coronal dimming is closely related with coronal mass ejections (CMEs). In particular, dimming areas in EIT 195 A images often match the lateral extension of the associated CMEs. In this presentation, we summarize how CMEs compare with dimming as identified at different wavelengths and by other instruments, such as Yohkoh SXT, TRACE, GOES (12-15) SXI, STEREO EUVI and SDO AIA. Emphasis is placed on recent data, since the combination of AIA and STEREO data can lead us to better characterize CMEs and to more accurately estimate how much mass is ejected. We discuss technical issues that arise when quantifying dimming as a proxy for a CME. The issues include instrument calibration, effects of heating and cooling and integration along the line of sight. We also touch on the relation of dimming with globally propagating coronal fronts, which are routinely isolated in running difference images, and its implications on the magnitudes of the associated CMEs.